The slip-on type pipe joints are so constructed as to enable the socket and the spigot to be joined together by inserting the spigot into the socket provided with a seal packing fitted in a packing receiving groove formed in the inner periphery of the socket while compressing the seal packing. There has been known such a slip-on type joint having separation preventive capability.
In the known separation preventive pipe joint, a locking ring receiving groove is formed at a location in the inner periphery of the socket deeper than the packing receiving groove, and a locking ring having one split in the circumference thereof is fitted in the locking ring receiving groove. Between the outer periphery of the locking ring and the inner periphery of the locking ring receiving groove is disposed an elastic ring for holding the locking ring with its axis concentric. On the outer periphery of the end portion of the spigot is formed a projection which is engageable with the locking ring from the deeper side of the socket. A small-diameter portion which is smaller in diameter than the locking ring receiving groove is formed in an inner peripheral portion of the socket at a location deeper than the locking ring receiving groove. The small-diameter portion has a given length along the axial direction of the pipe such as to permit the end portion of the spigot formed with the projection to be freely moved in the axial direction of the pipe between the locking ring and the deeper end of the socket, thereby imparting expansibility and retractability to the pipe joint.
With the construction of such a known separation preventive pipe joint, however, since the small-diameter portion having a predetermined diameter is formed from a peripheral edge of the locking ring receiving groove to the deeper end of the socket, the projection is likely to abut against the inner periphery of the small-diameter portion when the socket and spigot are bent relative to each other, particularly where the spigot is inserted up to the deeper side of the socket and hence the projection of the spigot is positioned close to the deeper end of the socket. This makes it impossible to impart sufficient bendability to the pipe joint.